Influence of selected operating conditions on starting spot width of test substance dissolved in solvent of high elution strength

The operational conditions for applying solutions of a dye (Oil Red) dissolved in acetone and methanol to a chromatographic plate are described. These solvents are characterized by high elution power, but they are very good solvents of various substances, so they are often used for this purpose in laboratory practice. However, their unfavorable feature, due to their use as solvents of samples placed on a chromatographic plate, is their high elution strength, which contributes to an increase of the diameter of the starting spot. To eliminate or reduce this unfavorable effect, this research used operational factors such as reduced speed of applying the test solution to the chromatographic plate, increased temperature (40 and 55 °C), and reduced pressure by 0.15 bar relative to atmospheric pressure. All this accelerated the evaporation of the solvents and led to smaller application spots. Studies have shown that the above-mentioned operational factors performed using equipment available in a regular laboratory contribute to a significant reduction of the starting spot despite the use of sample solvents with high elution strength.